Reproduction is of three types
(i) Vegetative By fragmentation, each fragment develops into thallus.
(ii) Asexual By spores, the most common is zoospore, they are flagellated for motility.
(iii) Sexual By fusion of gametes This can occur by one of the following types
(a) Isogamy When gametes are similar in size
(b) Anisogamy When gametes are dissimilar in size.
(c) Oogamy Fusion between one large non-motile female gamete and one small but motile male gamete.